German Patent Publication DE 2,423,454 C2 (Riha et al.), published on Apr. 3, 1975, discloses a leno selvage device for reinforcing the selvage by a so-called leno binding or leno weave. The known apparatus comprises a power driven leno disk having a rotational central geometric axis extending in parallel to the weft thread insertion direction in the loom. The leno disk is driven with the same r.p.m. as the r.p.m. of a carrier carrying leno thread supply spools. The leno disk has two eyelets arranged symmetrically relative to the central rotational axis of the disk.
The known leno device has two sections. One section is positioned on each side of the loom next to the respective warp threads. Both leno sections are driven through a coupling such as a gear belt connected to a drive wheel for a positive drive. The drive wheel is connected rigidly to a reduction gear shaft which in turn is driven by a reduction gear. The reduction gear with its shaft is coupled in a drive power transmitting manner with the main drive shaft of the loom.
For adapting the leno device of German Patent Publication DE 2,423,454 C2 to different weaving widths, the reduction gear shaft is coupled to a hollow shaft extending in the direction of the weaving width adjustment, namely in the direction of the weft insertion. A shaft section that drives the second leno device and the second leno spool holder is axially displaceable relative to the hollow shaft.
Deriving the drive power for both leno sections from the main loom drive requires a substantial number of drive components and hence is expensive. These drive components also require a substantial space in the loom and it is not possible to control the two leno sections independently of the main loom drive nor independently of each other.
German Patent Publication (DE-OS) 2,832,131 (Shindo et al.), published on Jan. 31, 1980, discloses a leno device for forming a leno selvage in a shuttleless loom, wherein the leno disk is part of a so-called satellite leno device. The leno disk has outer gear teeth meshing with other gears of the satellite gear drive of the leno device. The leno disk is rotatably mounted on a steady rest type carrier arm. The leno threads are pulled off from a spool rotor which is rotationally coupled to the leno disk. The leno threads pass through a substantially centrally located guide opening in the leno disk which additionally comprises two thread eyes positioned diametrically opposite each other in the leno disk. The threads pass through these thread eyes to the tie-up point along the selvage of the fabric.
The outer gear teeth of the leno disk mesh with the gear teeth of a drive gear wheel of the satellite gear drive which drives the leno disk and the respective leno spool holder in synchronism with each other.
German Patent Publication (DE-OS) 2,832,131 shows a drive shaft 44 for the satellite leno device and it is assumed that the drive power for the shaft 44 is derived from the main loom drive as is customary. As a result, the same drawbacks apply as have been mentioned above. Further, such conventional leno drives are not easily adapted to different weaving widths as is especially shown by German Patent Publication DE 2,423,454 C2 first mentioned above.
Conventionally, a relatively large space is required for the leno devices on the right-hand side and on the left-hand side of the loom shed formed by the warp threads. The conventional leno devices are arranged in the area of the rear shed which means that the number of heald shafts is limited by the position of the leno devices. Further, the length of the leno threads measured from the leno device to the tie-up point of the weft thread is relatively large. As a result, the leno front shed formed by the leno threads is relatively flat or rather the angle enclosed by the two leno threads is relatively acute, which has the drawback that it is not assured that each weft thread end is properly inserted into the leno shed.
Conventionally it is necessary to rotate the leno thread supply spool carriers to avoid twisting of the leno threads in the area of the rear shed. The twisting must be avoided because it can break the leno threads. The rotation of the leno thread spool carriers makes sure that untwisted leno threads are presented to the leno disk.